/**
* Name Server: 获取指定集群下的所有 topic
*/
public TopicList getTopicsByCluster(final String cluster, final long timeoutMillis)
throws RemotingException, MQClientException, InterruptedException {
GetTopicsByClusterRequestHeader requestHeader = new GetTopicsByClusterRequestHeader();
requestHeader.setCluster(cluster);
RemotingCommand request =
RemotingCommand.createRequestCommand(RequestCode.GET_TOPICS_BY_CLUSTER, requestHeader);
RemotingCommand response = this.remotingClient.invokeSync(null, request, timeoutMillis);
assert response != null;